Current commercial methods of producing TCP or TTCP are well known in the art. Different amounts of calcium source mixed with phosphate source using different techniques will produced either TCP or TTCP alone.
U.S. Pat. No. 4,891,198 on the preparation of TCP only shows that the addition of phosphoric acid to the calcium base will first resulted in the formation of hydroxyapatite, then towards monocalcium phosphate to dicalcium phosphate before finally being converted into tricalcium phosphate (TCP) slurry at pH between 8-12 and at reaction temperature of not less than 70° C. The reacted slurry was then spray dried to form TCP powder. Another method of producing TCP (U.S. Pat. No. 7,754,174) uses similar method as the above but with the addition of acetic acid to control the viscosity of the slurry during reaction, and the usage of double drum dryer to produce TCP powder. This method produces only small amount of powder (i.e. ˜72% water and ˜28% solid), but with higher production costs due to large amount of energy needed to operate the double drum dryer. Other methods of producing TCP powder alone were also described in U.S. Pat. Nos. 6,569,396, 5,011,495, 4,891,198, 4,717,556 and 5,679,294. These US patents taught almost similar techniques of producing TCP powder, but none shown to produce TCP and TTCP simultaneously.
European Patent No. 14732731 described a method of using starting formulations by mixing an aqueous calcium nitrate └Ca(NO3)2.4H2O┘ to an aqueous ammonium mono phosphate [(NH4)2HPO4] and ammonium hydroxide [NH4OH] before calcining the resulting mixture at a temperature of 800° C. to produce TCP. However this technique tends to form hydroxyapatite instead due to the temperature of the reaction system which is raised by the heat of the reaction. Other method of using starting formulations is described in U.S. Pat. No. 4,717,556 wherein hydrogen calcium phosphate, calcium carbonate [CaCO3] and water in the amount of 5-15 wt % solid concentrations and subjecting the slurry to the attrition mixing reaction. Despite this method requires the use of attrition reactor for efficient mixing, the reaction product still requires long ageing time process to form TCP.
The current methods of producing TTCP utilize a variety of formulations and techniques. U.S. Pat. No. 5,709,742 shows the method of calcining a calcium source and a phosphorus source at temperatures greater than 1400° C. and with the addition of alumina oxide [Al2O3] compound and forced cooling (greater than 10° C./min cooling rate) of the resulting product in the calciner furnace. This method, however, is technically difficult and easily causes damage to the refractory materials of the furnace due to rapid cooling process. U.S. Pat. No. 7,270,705 shows another method of producing TTCP only by reacting dicalcium pyrophosphate with calcium carbonate [CaCO3] in ethanol for 12 hours, followed by heating the mixture in an oven to dry the powder. The powder is then subjected to heating at 1400° C. to form TTCP. The use of ethanol, however, is highly critical due to its flammable nature and the need in this technique to dry it by oven heating. Small quantity TTCP production may not be critical, but for large scale TTCP manufacturing, it may be hazardous where the ethanol fume is being released into the air in large quantity continuously.
Other methods of producing TTCP powder alone were also described in various US Patents, such as for example, U.S. Pat. Nos. 5,536,575, 5,652,016, 5,569,490 and 4,891,198. These US patents taught almost similar techniques of producing TTCP powder, but none shown to produce TCP and TTCP simultaneously.
Therefore this invention shows the way to produce both TCP and TTCP at almost equal amount simultaneously. The combination of TCP and TTCP having specific particle size and with specific crystallographic structure provided a composite material, which will uniquely combine both chemical properties, as well as mechanical and resorbable properties of both materials. They can be applied in the fields of medical applications as bioresorbable bone graft materials, as fine chemicals, as column fillers for protein separation, as food supplement, and in agriculture as fertilizers.